1. Field of the Invention
The present invention relates to a process for preparing an alkylene oxide adduct of an organic compound having active hydrogen.
2. Discussion of the Related Art
Alkylene oxide adducts have recently become increasingly significant in such applications as surfactants, starting materials for toner binders, and anti-foaming agents. In addition, since the development of their applications and improvement in performance are expected, a process for preparing such alkylene oxide adducts at low costs is in demand. The most important alkylene oxide adducts are those in which an alkylene oxide is added to an alcohol, a fatty acid, an aliphatic amine, an aliphatic amide, or a fatty acid ester, the resulting alkylene oxide adduct constituting a very important group of nonionic surfactants.
The above alkylene oxide adduct may be prepared, for instance, by contacting the alkylene oxide with the organic compound having active hydrogen by a process comprising spraying an alkylene oxide to an organic compound having active hydrogen, or alternatively spraying an organic compound having active hydrogen to a reactor filled with an alkylene oxide; and carrying out addition reaction therebetween. In both cases, the alkylene oxide is added in accordance with the progress of the reaction process (semi-batch operation), and the reaction mixture in a state of liquid is stirred until a point where a desired amount of an alkylene oxide is reacted.
In addition, Japanese Patent Laid-Open No. Sho 55-49332 discloses a process for preparing an alkylene glycol monoether by using a fixed bed apparatus in which clay having a Montmorillonite structure exchanged with a particular cation is used as a solid catalyst.
This process has the following advantages:
1) An alkylene glycol monoether can be prepared in a high yield from an alcohol and an alkylene oxide; and
2) Since a solid catalyst is used, steps, such as separation of a catalyst and after-treatments, can be omitted.
However, since the process is involved with a liquidxe2x80x94liquid fixed bed reaction in which an organic compound having active hydrogen and an alkylene oxide are reacted in a state of liquid, the addition reaction dramatically proceeds at an inlet of the reactor. Therefore, in certain cases, there arise, for instance, the following problems:
1) A drastic temperature rise owing to the exothermic reaction by the addition of the alkylene oxide takes place, thereby resulting in an increase in pressure; and
2) Higher the proportion of the alkylene oxide to the alcohol, larger the amount of exothermic heat, so that the quality deterioration is likely to take place.
In addition, Japanese Examined Patent Publication No. Hei 7-2662 gives examples of a liquid-liquid fixed bed reactor using a similar catalyst as above. However, it is required that a large amount of a liquid is circulated, and that the amount of molar additions of the alkylene oxide is relatively controlled to a low level in order to suppress the exothermic heat and pressure increase upon reaction. In other words, in order to suppress exothermic heat and pressure increase, the amount of molar additions of the alkylene oxide should be relatively controlled to a low level, thereby consequently making it practically impossible to prepare an alkylene oxide adduct having a large number of molar additions. In order to prepare an alkylene oxide adduct having a large number of molar additions, the resulting reaction mixture can be circulated and reacted. However, in such cases, the production efficiency can be notably lowered.
In the addition reaction of the alkylene oxide by employing a fixed bed reactor, there have not been found an example where the number of molar additions is larger than those of these examples. This is because heat generated at an initial stage of reaction and pressure increase owing to the exothermic heat would be difficult to be overcome.
Japanese Patent Laid-Open No. Sho 52-151108 discloses an addition reaction of ethylene oxide using a conventional homogeneous base catalyst in a tube-type reactor having a mode of reaction similar to that of the liquidxe2x80x94liquid fixed bed reaction. This method is involved with a liquidxe2x80x94liquid homogeneous reaction, not a fixed bed reaction, the method having a mode of reaction similar to that of the liquidxe2x80x94liquid fixed bed reaction. This publication shows in its comparative examples that it is difficult to increase the number of molar additions of the alkylene oxide.
In Comparative Example 1 of the publication, it is disclosed that a higher alcohol having an average molecular weight of 208 adjusted to 170xc2x0 C. is fed to a reaction column having an inner diameter of 9.4 mm and a length of 25 m at a flow rate of 3.75 kg/hr, and ethylene oxide is fed from an inlet of the reaction column at a flow rate of 2.4 kg/hr. Under the above conditions, the highest temperature at 1.8 m from the inlet of the reaction column is 400xc2x0 C. or more, and the pressure is 100 kg/cm2xc2x7G or more, so that further continuation of the reaction becomes difficult, thereby making the resulting product to have brownish coloring and an extremely viscous state, impractical for actual use.
From the above results, in case of preparing by a liquidxe2x80x94liquid fixed bed reaction, an alkylene oxide adduct having the same level of a number of molar additions, i.e. 3 molar addition, as this comparative example, there can be easily deduced very high levels of exothermic heat at an inlet of the reaction column and a pressure increase caused thereby.
Accordingly, an object of the present invention is to provide a process for preparing an alkylene oxide adduct having excellent production efficiency without necessitating a high-level, pressure-withstanding equipment.
Another object of the present invention is to provide a process for preparing an alkylene oxide adduct with easy reaction control, thereby consequently making it possible to operate safely and stably by using a simple equipment.
These and other objects of the present invention will be apparent from the following description.
The present inventors have carried out addition reaction by a gas-liquid fixed bed reaction using a reaction column packed with a solid catalyst, and confirmed that improvements in production efficiency in a high-concentration catalyst reaction. They have found that by reacting an alkylene oxide in the state of a gas, the alkylene oxide concentration in the liquid can be made relatively uniform in the reaction column, so that no drastic exothermic heat and pressure increase incurred by the exothermic heat take place. Therefore, the gas-liquid fixed bed reaction can be operated safely and stably, and the present invention has been perfected thereby. Further, the present inventors have confirmed that in the preparation according to the conventional processes, when the number of molar additions of the alkylene oxide is high, the quality deterioration takes place owing to the reaction temperature rise by the exothermic heat, whereas in the process of the present invention, unexpectedly no quality deterioration of the resulting alkylene oxide adduct has been found.
The present invention pertains to a process for preparing an alkylene oxide adduct, comprising the steps of feeding an organic compound having active hydrogen and an alkylene oxide to a reaction column packed with a solid catalyst, and carrying out addition reaction of the organic compound having active hydrogen with an alkylene oxide in a gas-liquid fixed bed reaction, wherein the alkylene oxide is in a state of gas and the organic compound having active hydrogen is in a state of liquid.